Manufacture of sheets containing mineral wool fiber



' 45 substantial Patented Oct. 8, 1940 UNITED STATES 9 Claims.

This invention relates primarily to the manufacture of sheets containing mineral wool fiber as an essential or principal ingredient. While not restricted thereto, it deals more especially with the manufacture of mineral wool fiber sheets on machinery of the papermaking type.

Mineral or rock wool is available on the market in bulk form and consists 01' a mass of loosely aggregated fibers of various fiber lengths. Thus, one important grade of mineral wool contains fibers varying in lengthfromas short as a fraction of an inch, say about $41", to as long as several inches, say about 5". As will be appreciated by those skilled in the art, the formation of sheets from such mineral. wool on machinery of the papermaking type while largely or substantially preserving its fiber length presents a formidable problem, for, when'attempt is made to liberate of" segregate the mineral Wool fibers by manipulation as ordin'arily in the presence of water in a beater engine, the long-fibered component of the mineral wool is drastically reduced in fiber length or practically completely destroyed in arriving at a suspension or stock of adequate smoothness or uniformity for delivery to the papermalcing machine. Again, the mineral wool fibers tend under manipulation in water in the beater engine to develop fiber aggregates and refractory clumps or curly snarls, which, unless broken up by intensive beating action and attendant destruction of fiber length, yieldpoorly textured or wild sheets on a papermaking machine. The intensive or hard-beating of mineral wool fiber that is thus requisite for producing a smooth or uniform fiber suspension and the destruction thereby of the long fibers means that the sheets produced from such suspension are of extremely poor physical characteristics, such sheets being of low tear-resistance, fiexibility, and other physical qualities.

An objective of the present invention is to make possible the realization from stock containing-mineral Wool fibers as an essential or ingredient of uniformly textured sheets possessed of excellent physical characteristics, including relatively high tear-resistance, flexibility, porosity, resiliency, etc. Anotherobjective is to enable the manufacture of such sheets on machinery of the papermaking type while preserving substantially or to a very large extent the original fiber length and other characteristics of the mineral wool. A still further objective is to enable the production of such sheets with a substantial, preponderant,

' PATENT OFFICE.

Albert L. Clapp, 'Danvers, Mass.

No Drawing. Application January 19, 1938, Serial No. 185,784

-or substantially exclusive content of the mineral wool, thereby imparting to the sheet those qualities for which mineral Wool is prized, in-" cluding such qualities as low thermo-conductivity, fireproofness, inertness under weather- 5 ing influences, indestructibility by vermin and other pests, etc.

In accordance with the present invention, bulk mineral wool of the flufiy or voluminous character sold on the market is initially treated or 10 soaked with a slime or viscous solution which, while resistant to dilution or thinning out withwater, is nevertheless compatible with water and can under manipulation or working in the presence of water, as in a beater engine, be 15 diluted substantially uniformly with water to a non-viscous condition. I have found that when mineral wool is thus pretreated or presoaked, it can be readily resolved by manipulation in, water, as in a beater engine, into a smooth or go substantially uniform suspension of substantially completely liberated fibers while the fiber length of the original mineral wool is. substantially or to a very large extent preserved. It is evidently the case that the slime coats the in- 25 dividual fiber units and affords an excellent lubricant which tends to promote parting or segregation of the fibers as the lubricant temporarily resists dilution with water and, by temporarily imposing resistance against the fiber- 80 liberating or fiber-segregating forces exerted on the fiber mass by the beater engine or other manipulating instrumentality, enables sufiicient work or energy to be expended on the mass to accomplish the desired fiber-segregation or 85 liberation in a short period of time, that is, before the slime has been so diluted with water asto lose its original lubricating value and thus expose the mass in a condition such that its fibers tend to clump or snarl under manipula- 40 tion.

There are various slimes or aqueous gels that are useful for the pretreatment or soaking of mineral wool preparatory to'resolving such wool fibers while largely or substantially completely preserved .in fiber length into a. smooth pulp suspension in the presence of Water in a beater engine or equivalent apparatus and forming uniformly textured sheets from the suspension. 1 shall for the purpose of illustration cite typical slimes or gels that have been found to be eminently'satisfactory for the purposes hereof.

Example I Various fatty acid soap slimes or gels consist ing of aqueous soap solutions of a soap content upwards of about 1 /2% have been found suitable for use in the pretreatment or soaking of the mineral wool mass. A soap solution of heavy creamy consistency at room temperature may be prepared by admixing with oleic acid a caustic soda solution, sodium carbonate solution, or the like of such strength and in such amount as saponifles the oleic acid substantially completely and yields a solution of about 2% to 3%v sodium oleate content. The saponiflcation of=the oleic acid by the alkali solution may be hastened by heating the mixture to about 120 to 150 F. In order to promote rapid and thorough penetration of the resulting soap solution into the mineral wool mass, the solution is preferably applied thereto in hot condition, say, at about 120 to 150 F. The soap solution may be poured or otherwise applied onto the mineral wool mass, but a simple and effective procedure is to steep the mineral wool mass for a few minutes in the hot soap solution and then to remove-it in thoroughly soaked condition from the solution. If desired, the mineral wool mass may be held togather in a foraminous vessel or on a foraminous support while being steeped in and removed from the soaking bath. Once removed from the solution, excess or free solution may be permitted to drain from the mass. The mass thus soaked with soap slime may be permitted to cool before it is added to the beater engine and manipulated I in the presence of water as will hereinafter appear.

Example II Another slime or gel found to work satisfactorily in promoting the desired liberation or segregation of the mineral wool fibers is aqueous starch gel of a starch content upwards of about 2%. Specifically, an aqueous starch gel appropriate for the purposes hereof may be prepared by admixing raw potato starch, corn starch, or the like with water to form a starchsuspension of about 3% starch content and then adding sufficient caustic soda or equivalent alkali, say, about 7 to 10% of caustic soda, based on the weight of dry starch, to the starch suspension and stirring the mixture until substantially complete dissolution of the starch into a smooth limp gel has taken place. Such a starch gel or solution may be produced-readily at room temperature, but, before the mineral wool mass is treated with or dipped into such solution, the solution is prefererably heated to a temperature upwards of about 120 F so as to induce rapid and complete penetration of the mass and substantially uniform coating or envelopment of its fibers.

Example III Viscous glue or albumen solutions or gels represent still another class of media for properly conditioning the mineral wool mass prior to its manipulation in the presence of water inthebeat-.

er engine. Thus, an albumen gel satisfactory for the purposes hereof may be prepared by digesting or cooking under pressure 100 partsby weight of comminuted or ground scrap leather, 400 parts of water, and 15 parts of caustic soda until the leather is practically completely dissolved and then adding under heat and with agitation to the resulting solution sufficient water to form a glue solution of about 2 /2 to 5% dissolved leather content. The resulting glue solution is at room temperature of a consistency reminiscent of molasses and, at temperatures upwards of about 120 F.,

is sufliciently fluent to soak through and condition a mass of the mineral wool in but a few minutes.

-or gel, based on the dry weight of the mineral wool, be infused throughout the mineral wool mass, since it is essentially only upon the slime or gel that fiber-liberation or segregation in the beater engine with the desired preservation of fiber length depends; and suflicient slime or gel must be present during beating or manipulation in the presence of water for the purpose of ensuring the desired substantially complete liberation of the fibers while largely or substantially completely preserving original fiber length. However, less slime or gel need be used when cellulose pulp, asbestos, or thelike is to be blended with the mineral wool fiber in the beater engine, since pre-beaten orthoroughly slushed cellulose fiber, asbestos, or the like, to which the slime-treated mineral wool fiber is added, tends to promote somewhat the liberation of the fibers of the slime-treated mineral wool. It should, however, be understood that cellulose fiber, asbestos, or the like does not and cannot by itself perform the function of promoting the liberation of the mineral wool fibers at substantially their original fiber length. On the contrary, when a mass of mineral wool lacking the conditioning slime is blended with as much as to 90%, based on the weight of the blend, of cellulose and/or asbestos fiber, pronounced difliculty is encountered in liberating the mineral wool fibers, insomuch that sizable clumps or snarls of the mineral wool fibers persist until the original fiber length of the mineral wool has been very greatly reduced or largely destroyed. Besides performing the function of inducing individualization of the fibers in a mineral wool mass pretreated therewith, the slime is also of value in accelerating uniform blending of the liberated mineral wool fibers with cellulose fiber, asbestos fiber, or the like in the presence of water in the beater engine.

In producing sheets or boards of mineral wool designed for use as thermo-insulation in buildings, refrigerators, and other structures, it is usually desirable that the sheets or boards contain more or less cellulose fiber, which is of value in that it increases the strength and rigidity of the sheets or boards. While various kinds of cellulose fiber, including waste papers, groundwood pulp, kraft pulp, sulphite pulp, or the like may be employed as the cellulose fiber constituent of the finished sheets, sulphite pulp screenings and/or kraft pulp screenings constitute a satisfactory low-cost source of cellulose fiber. In producing sheets or boards from ablend of sulphite pulp screenings and the slime-soaked mineral wool mass, it is important to reduce the screenings to the desired fineness and smoothness before the slime-soaked mineral wool mass is added thereto and the mixture manipulated until the mineral wool fibers have been individualized or liberated. To this end, the procedure may involve preheating thoroughly the sulphite pulp screenings, as in a hollander and/or jordan, and then adding to the well-beaten cellulose stock in the beater engine the slime-pretreated mineral wool while the knives of the beater roll are raised sufficiently from the bed-plate of the engine so that they exercise little more than a mere brushing action on the stock and circulation or mixing of the stock. The slime-pretreated mineral wool is preferably fed into the beater engine immediately in front of the beater roll so that its first pass through the clearance between the beater roll and the bed-plate follows quickly upon its addition to the engine and is attended by considerable, although not complete, segregation or individualization of the mineral wool fibers. The rapidity with which the mineral wool fibers are individualized or liberated can be best appreciated from the fact that, working with blended stool: containing about 50% to 80% of the mineral wool fiber, the smooth pulp suspension blesired for delivery to a papermaking machine can be realized in a period as short as about 10 to 15 minutes, in the course of which-time very little reduction of the'fiber length of the mineral wool occurs. The fact is that only some of the very longest mineral wool fibers are cut or reduced in length, but such fiber-cutting or reduction as does take place is confined essentially only to fibers of several inches length; and the cutting of such fibers is desired so as to enable the desired uniform felting of the resulting smooth pulp suspension on the papermaking'mw chine. Of course, manipulation of the fiber. blend in water in the beater engine may be continued for a longer period of time without material.

injury to the mineral wool fibers, since the beater roll is operated under conditions to do no more than to brush and mix or circulate the stock. Most or practically all of the individualization or liberation of the mineral wool fibers occurs during the first few minutes of mixing or manipulation in the beater engine, that is, while the slime envelopes on the mineral wool fibers have not as yet been leached from the fiber surfaces and diluted by the relatively large amount of water present in the beater engine during beating. Once the'slime has been removed from the mineral wool fibers, that is, has been diluted by the beater water, it no longer promotes-individualization or liberation of the mineral wool fibers, as can be seen from the fact that when the raw mineral wool mass is efiected in plain water. Accordingly, once the fibers of a mineral wool fiber mass have been individualized in the beater engine by the process hereof, there is no point in further manipulation of the resulting suspension by beater action. It might be further noted that, when a mass of raw mineral wool is added to an already-individualized mineral wool fiber suspension producedby the process hereof, very little individualization or liberation of the fibers ofsuch raw mineral wool mass occurs; and the fibers of such mass simply float or are diffused in balled-up or clumpy condition throughoutthe suspension.

-When soap or other precipitable slime, such as viscose syrup or sodium silicate, is used in the process hereof for pretreating the mineral wool mass, it maybe desirable to add alum or other precipitant for the slime to the mineral wool fiber suspension just before operation of the beater engine is stopped. The alum serves to precipitate the fatty acid soap on the fibers as an aluminum-iatty-acid compound, which is a binder or size in the sheets fabricated from the fiber suspension. If desired, various sizes, such as rosin,

rubber latex, aqueous emulsions of bitumen,

resins, waxes, or the like may be. added to the fiber suspension and precipitated by alum or the like onto the fibers before the suspension is delivered to the papermaking machine. The addition of such sizes or binders together with alum is preferably made to the stock or fiber suspension after the mineral wool fibers therein have been practically completely individualized or liberated and just before operation of the beater I engine is stopped, thereby avoiding such undesirable effect as the size and/or alum might have on the fiber-individualizing activity of the slime associated with the mineral wool fibers.

When sulphite pulp screeningsor other cellulose fiber exhibiting an acid condition in water is to be blended with the mineral wool fibers, it is distinctly preferable to add sumcient alkali to such fiber before the slime-treated mineral wool is mixed therewith. Otherwise, the acidic constituents in the beater water tend to react with the slime and to modify it to such an extent that such alkaline slirnes or gels are used in pretreating the mineral wool to be blended with cellulose fiber stock in the beater engine, it is desirable that such latter stock; especially when originally acid, be put distinctly on the alkaline side, for instance, be treated with suflicient caustic soda or other alkali to exhibit a pH value of 7.5 to 8 or higher.

The mineral-wool-fiber-containing stocks or fiber suspensions produced by the process hereof may be formed into relatively thin paper sheets of uniform texture on paper making machines, in which case the paper sheet is sufilciently flexible to be used for suchpurposes as being wound as insulation material to the desired thickness or number of layers about steampipes or the like to be thermo-insulated. The thin sheets may also be impregnated with various binders, such as artificial resins, and laminated under heat and pressure into boards of considerable thickness and rigidity. In such latter case, it is usually desirable to avoid precipitation and retention of the slime with which the mineral fiber mass is originally treated, thereby producing substantially unsized sheets that are highly absorptive and hence readily impregnated or' saturated with binders. When no alum or other precipitant is used in the beater engine to precipitate the,soap

or other slime or when starch or albumen gel is sheet consists practically exclusively of the min- .75

comparison with mineral wool.

mal fiber, which is inert toward various chemical solutions. So, too, the mineral-wool-fiber-containing suspensions produced by the process hereof may be sheeted on board-forming machines, such as wet machines or multi-cylinder machines. The resulting boards, which may already contain various sizes or binders, may be impregnated, if desired, with various binders, such as artificial resins, waxes, rubber latex, sodium silicate, or the like to afford finished boards of considerable stiifness and strength. It might be noted that boards formed by the process hereof with little, if any; content of cellulose fiber are characterized by their light-weight quality, resiliency, and high porosity, particularly when little or no binder has been infused thereinto either deliberately or through the use of the slime, and are also capable of being rapidly and uniformly impregnated with a largeamount of binder. The foregoing qualities also inhere to a large extent in boards containing only about 10% to 25% by weight of. cellulose fiber, based on the dry weight of their total fibrous components, but the incorporation into the boards of, say, about 50% or more of wellbeaten cellulose fiber, such as well-beaten sulphite pulp screenings, tends to stiffen the boards markedly and to detract considerably from their resiliency, even though they still display high porosity or absorptivity in the absence of any appreciable content of size. In lieu of the cellulose fiber component of the boards, asbestos fiber may be employed, in which case the resulting boards are fire-proof. Unlike an all-asbestos board, however, boards produced by the process hereof with a mineral wool fiber content upwards of about 25% are, in the absence of any appreciable content of size, very porous and absorptive by reason of the tendency of the mineral wool to form fiufiy or loose-textured sheets as contrasted with the tendency of asbestos to felt densely. The foregoing is probably attributable to the high density or specific gravity of the asbestos in In this latter connection, it might be observed that even shortfibered mineral wool tends to form a bulky or spongy sheet, but the sponginess or bulkiness as well as the strength of a mineral fiber sheet is, of course, increased through the preservation by the process hereof of the mineral wool fibers at maximum length, for instance, at a length ranging from a fraction of an inch to several inches and hence corresponding essentially to the fiber length of the raw or original wool fiber mass.

It is possible to blend animal fiber or hair, such as long-fibered cattle hair, with the aqueous mineral-wool-fiber suspensions produced by the process hereof and to form from the resulting stock finished felts or sheets of unusually high sponginess, resiliency, flexibility, etc. is that the principles of the present invention are advantageously applicable to long-fibered animal hair, as well as to mineral wool, and to longfibered cellulosic fibers, such as sisal, manila, etc. That is to say, when long-fibered animal hair or cellulosic fiber is to be blended with the mineral wool fiber suspensions produced by'the process hereof, it may be desirable to condition the longfibered hair or cellulosic fibers preparatory to its manipulation and suspension in water in the beater engine in very much the same way as the mineral-wool-fiber masses are conditioned pursuant to the present invention. Thus, assuming that it is desired to incorporate a substantial percentage of long-fibered cattle hair, say, about 10% or more of such hair, into the aqueous min- The fact eral-wool-flber-containing suspensions hereof, and thereby to arrive at a stock to be formed into finished sheets or boards of extremely high sponginess, good tear-resistance and other physical properties, high thermo-insulating value, etc., the practicemay be to presoak the mass of animal hair with slime or gel, as hereinbefore described, prior to its being manipulated in water inthe beater engine and thereby to produce an individualized animal-hair suspension wherein the length of the original hair fibers has been very largely or substantially completely preserved. The resulting aqueous suspension of substantially individualized hair fibers may then be admixed with the aqueous suspension of substantially individualized mineral wool fibers produced ciable amount of the mineral wool but containing, if desired, short-fibered cellulose, asbestos, sizing agents, or. other ingredients, as hereinbefore described. The present invention may also be utilized in instances when the substantially individualized long-fibered pulp suspensions hereof are formed into sheets or boards on other than papermaking machinery, for instance, in molds or presses of the various types well known to those skilled in the art. It should be understood that the expression mineral wool as used herem should be construed in its comprehensive sense as including the various mineral wools of commerce, for instance, those designated as rock wool, slag wool, glass wool, etc.

I claim:

1. A process which comprises treating a mass of aggregated mineral wool fibers with aqueous viscous slime of at least about 1 content of sliming agent so as to coat the fiber substantially uniformly with the slime in amount of at least about 200%, based on the dry weight of said mass; and mixing and agitating the slime-treated mass in a relatively large amount of water to liberate substantially completely the fibers of said mass and thereby to produce an aqueous suspension of the substantially completely liberated fibers.

2. A process which comprises treating a mass of aggregated mineral wool fibers with aqueous slime of at least about 1 content of sliming agent so as to coat the fiber substantially uniformly with the slime in amount of at least about 200%, based on the dry weight of said mass, said slime being compatible with water but being so viscous as to resist dilution with water; and mixing and agitating the slime-treated mass in a relatively large amount of water to liberate substantially completely the fibers of said mass and thereby to produce an aqueous suspension of the substantially completely liberated fibers.

3. A process which comprises treating a mass of aggregated mineral wool fibers with a viscous, water-compatible, aqueous slime of at least about l content of sliming agent so as to coat the fibers substantially uniformly with the slime in amount of at least about 200%, based on the dry weight of said mass, subjecting the slimetreated mass to beater action in the presence of a relatively large amount of water to liberate substantially completely the fibers of said mass and thereby to produce an aqueous suspension of the substantially completely liberated fibers, said beater action being controlled to preserve largely the original fiber length of said fibers in the course of their liberation and suspension in water, and sheeting the fibers from the resulting aqueous suspension on a papermaking machine.

4. A process which comprises soaking a mass of aggregated mineral wool fibers with at least about 200% of its dry weight of a viscous, waterdilutable, aqueous slime containing at least about 1 /2% of sliming agent capable of being precipitated onto said fibers, subjecting the slime-soaked mass to beater action in the presence of a relatively large amount of water to liberate substantially completely the fibers of said mass and thereby to produce an aqueous suspension of the substantially completely liberated fibers, said beater action being controlled to preserve largely the original fiber length of said fibers in the course of their liberation and suspension in water, precipitating the diluted slime onto said fibers in aqueous suspension, and sheeting the fibers from said aqueous suspension on a papermaking machine.

5. A process which comprises soaking a mass of aggregated mineral wool fibers with at least about 200% of its dry weight of an alkaline, viscous,

- to liberate substantially completely the mineral wool fibers and thereby'to produce an aqueous suspension of the substantially completely liberated mineral wool fibers in substantially uniform admixture with the cellulose fibers, said beater action being controlled to preserve largely the original fiber length of said mineral wool fibers in the course of their liberation and suspension in water, and sheeting the substantially uniformly mixed fibers from the resulting aqueous suspension on a papermaking machine.

6. A process which comprises treating a mass of aggregated mineral wool fibers with aqueous viscous slime of at least about 1 /2% content. of sliming agent so as to coat the fibers-substantially uniformly with the slime in amount of at least about 200%, based on the dry.weight of said mass, incorporating the slime-treated mass into an aqueous suspension of substantially completely liberated fibers other than mineral wool, and mixing and agitating the mixture until the mineral wool fibers have been substantially completely liberated and an aqueous suspension of substantially uniformly mixed fibers results, said mixing and agitating operation being controlled to preserve largely the original fiber length of said -mineral wool fibers.

7 A process which comprises soaking a mass of aggregated mineral wool fibers with at least about 200% of its dry weight of an alkaline, viscous, water-dilutable, aqueous slime containing at least about l /2% of sliming agent capable of being precipitated onto said fibers, incorporating said m'assinto an. aqueous suspension of alreadybea en, intrinsically acid cellulose fibers alkalinize ito a distinctly alkaline condition, subjecting 8. In a process of producing from a mass of aggregated fibers an aqueous suspension of substantially completely liberated fibers capable of being felted from such suspension into a substantially uniformly textured sheet on a papermaking machine, those steps which comprise soaking the masswith aqueous slime containing at least about 1 of a sliming agent, amounting to at least about 200%, based on the dry weight of said mass, and capable of being diluted with water but so viscous as to resist dilution; and mixing and agitating the slime-soaked mass in a relatively large amount of water until the fibers of said mass have been substantially completely liberated to yield said aqueous suspension,

.said mixing and agitating operation being controlled to preserve largely the original fiber length of said mass of aggregated fibers.

9. In a process of producing from a mass of aggregated fibers an aqueous suspension of fibers capable of being felted from such suspension into a substantially uniformly textured sheet on a papermaking machine, those steps which comprise soaking the mass with an aqueous alkaline slime containing at least about 1 /2% of a sliming agent, amounting to at least about 200%, based on the dry weight of said mass, and capable of being precipitated onto the fibers and capable of being diluted with water but so viscous as to resist dilution, mixing and agitating the slimesoaked mass in a relatively large amount of water until the fibers of said mass have been substantially completely liberated to yield said aqueous suspension, said mixing and agitating operation being controlled to preserve largely the original fiber length of the mass of aggregated fibers, and precipitating the water-diluted slime with an acidic reagent onto the fibers of the resulting aqueous fiber suspension.

ALBERT L. CLAPP. 

